Optical transmitter using two or more optical sources

Abstract

The transmitter comprises two optical sources (201, 202) simultaneously supplied with modulation current in series, whereas they are separately supplied with DC bias current. The separation between the modulating currents of the two optical sources is realized by means of inductances (214, 215, 227). A first optical source (201) receives on its anode the modulation signal coming from an input (216) and then emits the modulation signal to the second optical source (202) via a coupling capacitor (226) between the two optical sources.

What is claimed is:  
     
       1. An optical transmitter intended to transmit an optical signal through a broadband transmission network including at least one optical fiber that transports an optical signal from a transmitter to at least one optical receiver, the optical transmitter including at least two optical sources arranged in series and driven simultaneously, wherein the transmitter includes means for separately supplying DC bias current to the optical sources and for supplying AC modulation current to them in series, while the separate DC currents biasing the optical sources flow via at least two inductances that have a value that is sufficient to practically block the flowing of the AC modulation current, and wherein the two optical sources are directly connected in series, and in that the transmitter includes a push-pull arrangement whose output is connected to the common point between the diodes, so as to add or take out current from one of the diodes. 
     
     
       2. An optical transmitter as claimed in  claim 1 , characterized in that it includes a coupling capacitor between the two optical sources, a first optical source receiving the modulation signal on one of its electrodes and then transmitting the modulation signal to a second optical source by means of said coupling capacitor. 
     
     
       3. An optical transmitter as claimed in  claim 2 , characterized in that it includes an inductance ensuring the return to ground of the DC current polarizing the first optical source. 
     
     
       4. An optical transmitter as claimed in  claim 1 , characterized in that the optical sources are laser diodes. 
     
     
       5. An optical transmitter as claimed in  claim 1 , characterized in that the optical sources are light-emitting diodes. 
     
     
       6. An optical transmitter as claimed in  claim 1 , wherein the transmitter includes means for comparing the optical modulation signal emitted by the first optical source with a suitably delayed replica of the signal present on the input of the transmitter in order to generate an error signal proportional to the distortion and the noise affecting the optical signal emitted by the first optical source and means for feeding the second optical source with the sum of the error signal and the signal to be transmitted, means for delaying the latter so as to correct as exactly as possible the signal emitted by the first optical source, and means for combining the optical signals coming from each of the two sources after the addition of a suitable delay, by means of an optical coupler intended to feed the optical signal transmission network. 
     
     
       7. An optical transmitter as claimed in  claim 6 , characterized in that it includes means for adjusting the amplification of the error signal.